One of the main problems of ML researchers is in getting hold of real data.
I got this note from Mehta Krishna, co-founder of Thinkalytics:
Check out another datamining competition to keep you busy after the KDD CUP @ www.hearstchallenge.com . $30k in prize money and a lot of fun!
This is an interesting contest, where the task is to classify user reaction to emails.
Release date for the actual dataset is June first. Submission is Aug. 31.